High performance engines require quick response times. The drive transmissions must shift speeds quickly to provide optimum performance. This is particularly true in racing situations, for example in snowmobile racing.
The infinitely variable drive pulley for belt drive transmissions commonly found in snowmobile engines is well known. A key part of the clutch system in those transmissions is the actuator lever or shifter which operates as a cam relative to a fixed roller by pivoting about a pivot point on an axially moveable sheave so that in response to centrifugal force the axially moveable sheave of the system is urged towards a axially fixed sheave to thereby transfer rotation to the axially fixed sheave.
Particularly in race conditions, fast clutching and de-clutching is imperative. Therefore, faster response clutches are constantly being pursued. However, the clutches currently being used do not clutch and de-clutch fast enough to provide the racer with optimum performance from the engine. It is believed that these clutches lack the proper weight distribution below the pivot point to provide peak performance throughout the shift.
Attempts to improve clutch performance in the prior art have largely focused on the engagement point of the actuator. For example, U.S. Pat. No. 5,326,330 of Bostelmann, issued Jul. 5, 1994, describes an infinitely variable drive pulley for a belt drive transmission which uses an adjustment eccentric on the adjusting lever of the assembly to adjust the centre of gravity of the lever relative to the pivot pin and the initial position of the cam surface relative to the follower when in the rest or neutral position. This, in theory, varies the engagement speed of the clutch. However, once the clutch is engaged, the weight distribution of the lever does not change as the pulley moves from the rest or neutral position through the shift to the full shift position. Therefore, clutch performance and engine performance are ultimately compromised.
Other attempts at using specialized actuators have been directed toward different clutch assemblies or transmission systems and would therefore not function in the infinitely variable drive pulley system. Reference may be had, for example, to U.S. Pat. No. 771,771 of Dysterud, issued Oct. 4, 1904 and U.S. Pat. No. 2,647,604 of Carmichael, issued Aug. 4, 1953.
There therefore exists a need for a clutch actuator which operates at higher engagement speeds and which allows for weight distribution within the shift.